my 2020 GMC Sierra 1500 goes dead, after driving to Montana and home, after 2 days non use!!

[Mike T in MN]

can anyone help? This has been a recurring problem, truck battery is drained. It has been tested no less than 4 times for parasitic drain, battery etc.......

I charged the battery last night and this morning it wouldn't start, just dead, dash all lit up, alerts popping up, radio working, when I closed the door the dash was still all lit up, radio wouldn't turn off, no ignition...locked the doors and was still lit up inside.....HELP!!

Mike

 

[64BAwagon]

Assuming the parasitic tests on the truck come back negative and youre certain that nothing was left on in the truck you have no other suspect than the battery. To know for sure you would need to charge the battery (out of the truck) and then load test it. 

[Phantom 4D]

18 minutes ago, 64BAwagon said:

Assuming the parasitic tests on the truck come back negative and youre certain that nothing was left on in the truck you have no other suspect than the battery. To know for sure you would need to charge the battery (out of the truck) and then load test it. 

Agree. However, remember that the charging system on these trucks are ECM controlled. So the alternator is probably good. I would strongly suggest checking the ECM relay. If it's sticking, it will cause the problem you describe. To determine if it's bad, swap it with another relay. Easy to do since relays are pretty much all the same. 

[richard wysong]

The fact that everything was still working other than the starter tells me it is not a battery issue. Any codes? VATS light? Maybe a communication problem between BCM PCM, where everything stayed on maybe a ground problem. HMI module?

Edited January 13, 2023 by richard wysong

[64BAwagon]

Its hard to say since the details of the "4 times" it has been tested are unknown.  I always start with the cheap and easy stuff first and then work from there. Assuming the voltmeter hasnt shown low, the next step is proving the battery is any good. If it was charged overnight while in the truck and still wouldnt start then based on that I am instantly suspect of the battery. 

Stuff like this is a process of elimination. Battery cables and everything else are always suspect. 

[richard wysong]

Welcome to the Forum!

[richard wysong]

Does it start with a jump?

[richard wysong]

Similar problems have been attributed to bad connections/ corrosion in the underhood fuse box on the ECM power supplies